AD9467 Native FMC Card / Xilinx Reference Design

Introduction

The AD9467 is a 16-bit, monolithic, IF sampling analog-to-digital converter (ADC) with a conversion rate of up to 250 MSPS. This reference design includes a data capture interface and the external DDR-DRAM interface for sample storage. It allows programming the device and monitoring its internal status registers. The board also provides other options to drive the clock and analog inputs of the ADC. This can be done by programming the AD9517-4 clock chip and/or setting up the ADL5565 differential amplifier respectively.

Evaluation Board Hardware

To find out more information about the evaluation board hardware, default operation and jumper selection settings please read the Evaluation User Guide of the board. (UG200)

Clock Selection

The default clock input circuitry is derived from a simple transformer-coupled circuit using a high bandwidth 1:1 impedance ratio transformer (T201) that adds a very low amount of jitter to the clock path. The clock input (J201) is 50 Ω terminated and ac-coupled to handle single-ended sine wave types of inputs. The transformer converts the single-ended input to a differential signal that is clipped before entering the ADC clock inputs.

The evaluation board can be set up to be clocked from the crystal oscillator, Y200. This oscillator is a low phase noise oscillator from Vectron (VCC6-QCD-250M000). If this clock source is desired, install C205 and C206 and remove C202. Jumper P200 is used to disable the oscillator from running.

A differential LVPECL or LVDS clock driver can also be used to clock the ADC input using the AD9517. Populate C304, C305, C306, and C307 with 0.1 µF capacitors for one drive option or the other and remove C209 and C210 to disconnect the default clock path inputs. The AD9517 has many SPI-selectable options that are set to a default mode of operation. Consult the AD9517 data sheet for more information about these and other options.

Please make sure you have removed or inserted the corresponding components on the board to select the desired clock path. The schematic of the board can be found at the Download section.

Supported Carriers

Other Required Hardware

Required Software

We're upgrade the Xilinx tools on every release. The supported version number can be found in our git repository .

A UART terminal (Tera Term/Hyperterminal), baud rate 115200.

Using the HDL reference design

Instruction about how to build the HDL design and generate a bit stream, can be found here.

Functional description

The reference design is built on a ARM/Microblaze based system tailored for Linux. A functional block diagram of the design is given below.

Through an SPI interface, the software can access the AD9467/AD9517-4 registers, given the possibility to initialize and configure the ADC and/or clock chip.

The LVDS interface captures and buffers data from the ADC. The DMA interface then transfers the samples to the external DDR-DRAM. The capture is initiated by the software. The status of capture (overflow, over the range) are reported back to the software.

Good To Know

The PN9/PN23 sequences are not compatible with O.150. Please use the equations given in the reference design. They follow the polynomial equations as in O.150, but ONLY the msb is inverted.

The AD9467 drives the interleaved first byte (D15:D1) on the rising edge and second byte (D14:D0) on the falling edge of DCO clock. However in certain frequencies the captured data (from IDDR) seems to be reverse. If that occurs try setting the “capture select” bit (register 0x0a, bit 0).

Using the Software Reference Design

The Software Reference Design contains an example on how to:

Initialize the AD9467 evaluation board

Initialize the AD9467 HDL core

Test the ADC communication using the test patterns and PRBS sequences generated by the AD9467

Capture data from the AD9467 using DMA transfers

The software project contains 3 components: the AD9467-FMC-EBZ reference design files, the AD9467 driver and the AD9517 driver. All the components have to be downloaded from the links provided in the Downloads section.

AD9467 Software Driver

Below is presented a short description of all the functions provided in the driver.

Function

Description

int32_t ad9467_setup (int32_t spiBaseAddr, int32_t ssNo)

Configures the test mode and the output mode to a default state. Receives as parameters the SPI peripheral AXI base address and the slave select line on which the slave is connected. Returns negative error code or 0 in case of success.

int32_t ad9467_write (uint16_t regAddr, uint8_t regVal)

Writes data into a register. Receives as parameters the address of the register to be written and the value to be written into the register. Returns 0 in case of success or negative error code.

int32_t ad9467_read (uint16_t regAddr)

Reads data from a register. Receives as parameter the address of the register to be read and returns the read data or negative error code.

int32_t ad9467_pwr_mode (int32_t mode)

Configures the power mode. Receives as parameter the power mode and returns the negative error code or the set power mode.

int32_t ad9467_test_mode (int32_t mode)

Sets the ADC's test mode. Receives as parameter the ADC test mode and returns the set test mode or negative error code.

int32_t ad9467_reset_PN9 (int32_t rst)

Sets (1) or clears (0) the reset short PN sequence bit(PN9). Returns the negative error code or the set PN9 status.

int32_t ad9467_reset_PN23 (int32_t rst)

Sets (1) or clears (0) the reset long PN sequence bit(PN23). Returns the negative error code or the set PN23 status.

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